[darcs-users] how to redistribute darcs+Eclipse (was: Darcs API?)

[zooko at zooko.com]

P.S.  I am not a lawyer.  This letter I wrote (quoted below) was not legal
advice.  If you were to act on ideas you got from reading that letter, and
harm were to result from your act, then this would be your problem and not
mine.

--Z

> 
> There is another issue here aside from the common question of whether your
> code ought to be GPL'ed or not.
> 
> You could take Eclipse and GPL'ed darcs and combine them into one combined
> package and redistribute it, except for the "patent retaliation clause" which
> makes EPL incompatible with GPL.
> 
> The Eclipse Public License is GPL-incompatible *only* because of it has a
> clause disallowing people from using Eclipse while suing other people for
> patent infringement of a patent that applies to Eclipse.  The GPL requires
> that you allow other people to use the software freely (even if those people
> are currently suing you for patent infringement).  Therefore, you cannot
> redistribute a combined work comprising a GPL'ed component (use this combined
> work freely, even if you are suing me for patent infringement of a patent that
> applies to this software) with an Eclipse component (use freely, unless you
> are suing me for etc.),
> 
> If the copyright holders of darcs wanted to allow people to distribute Eclipse
> combined with darcs, they could amend the darcs license with a "special
> exception" that says you are allowed to redistribute darcs combined with
> EPL'ed software.  This would not, as far as I know, violate the intent of
> David Roundy and the others that darcs be GPL'ed.  In particular, doing this
> would *not* allow darcs to be used as a module in a proprietary combined work.
> 
> See for example the FSF's recommendation about making a special exception for
> QPL'ed programs in [1].
> 
> Another workaround would be if the FSF ever got off its great big glacial butt
> and published a new version of the GPL.  Since the license of darcs states
> that people may use it under GPL v2.1 or at their discretion any later
> version, people could then use darcs under this hypothetical new version of
> the GPL.  The next version of the GPL will hopefully be compatible with the
> EPL, which would then allow people to start redistributing Eclipse combined
> with darcs with no further effort on the part of the authors of darcs.  The
> reason I have this hope is that the FSF states on their "license list" page
> [1] that they have no objection in principle to Eclipse's "patent retaliation"
> clause.
> 
> So in short, darcs *could* be legally combined with Eclipse if either (a) the
> copyright holders of darcs said so in a legally binding way or (b) the FSF
> published a new version of GPL which was compatible with EPL.
> 
> In the meantime, you are still allowed to *use* Eclipse combined with darcs on
> your own system, you are just not allowed to redistribute it to other people.
> 
> Regards,
> 
> Zooko
> 
> [1] http://www.fsf.org/licensing/licenses/license-list.html
> 
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